Referring to FIGS. 1 to 3, U.S. Pat. No. 6,810,780 discloses a conventional positioning device 1 adapted for use in a miter saw 15. The miter saw 15 includes a base seat 151, and a working table 152 that is rotatably mounted to the base seat 151. The working table 152 has a body portion 153 and a mounting portion 154 that is connected to the body portion 153. The conventional positioning device 1 includes a scale disc 11, an elastic member 12, a linking member 13, and a lever member 14.
The scale disc 11 is disposed below the body portion. 15:3 of the working table 152, and is formed with a plurality of notches 111. The elastic member 12 has two fixing portions 121 connected fixedly to the body portion 153 of the working table 152, a movable portion 122 opposite to the fixing portions 121, and a protruding portion. 123 connected to the movable portion 122 and adapted to removably engage one of the notches ill of the scale disc 11. The linking member 13 has a cylindrical rod portion 131, and a coupling portion 132 connected to the rod portion 131 and removably connected to the mounting portion 154 of the working table 152. The lever member 14 has a biasing portion 141 abutting against the movable portion 122 of the elastic member 12, two opposite extension portions 142 connected to the biasing portion 141, two pivot portions 143 respectively connected to the extension portions 142 and rotatably connected to the rod portion 131 of the linking member 13, a handle portion 144 opposite to the biasing portion 141 and connected to the extension portions 142, and two reinforcing portions 145 connected to the biasing portion 141. The handle portion 144 is operable to drive movement of the biasing portion 141.
When the protruding portion 123 of the elastic member 12 engages one of the notches 111 of the scale disc 11, the working table 152 is non-rotatable relative to the base seat 151. When the handle portion 144 is downwardly pressed, the biasing portion 141 is moved upwardly to drive the movable portion 122 of the elastic member 12 to move away from the scale disc 11, so as to disengage the protruding portion 123 of the elastic member 12 from the one of the notches 111, and to thereby permit rotation of the working table 152 relative to the base seat 151.
However, each of the pivot portions 143 of the lever member 14 is required to be drilled to form a hole for retaining a respective end of the rod portion 131 of the linking member 13. Likewise, the mounting portion 154 of the miter saw 15 is required to be drilled to form threaded holes so that the coupling portion 132 can be threadedly secured to the mounting portion 154 with screws (not shown). Such configurations of the linking member 13 and the lever member 14 render the manufacturing and assembling of the conventional positioning device 1 relatively complicated.